Railway traffic controlling apparatus



R. K. CROOKS RAILWAY TRAFFI C GONTROLL I NG APPARATUS March 24, 1942.

4 Sheets-Sheet" l HIS ATTORNEY Filed Feb. 25, 1941 March 24, 1942.

R. K. CROOKS.

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Feb. 25, 1941 4 Shets-Sheet2 .AAM

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AAAAA vvvvv INVENTOR Halpjflraokr. BY

HIS ATTORNEY March 24, 1942. R, K, CROOKS RAILWAY TRAFFIC CONTROLLINGAPPARATUS Filed Feb 25, 1941 4 sheets-sheets am Paw CA LQN \mwm EN XWMMWEEBSQ Q h L wm INVENTOR Hal p12 POOliJ.

MS ATTO RN EY March 24', 1942. K. CROOKS RAILWAY TRAFFIC CONTROLLINGAPPARATUS Filed Feb. 25, 1941 4 Sheets-Sheet 4 1' IINVENTOR 15([5ATTORNEY Patented Mar. 24, 1942 v pmrso STATES PATENT OFFICE RAILWAYTRAFFIC CONTROLLING APPARATUS Ralph K. Crooks, Sharpsburg, PaL,assignorto The Union Switch & Signal Company, Swissvale, Pa., acorporation oi Pennsylvania Application February 25, 1941, Serial No.380,416

18 Claims.

a plurality of characteristics in addition to the rate of interruption,a distinctive characteristic Several different code rates are requiredwhen several diilerent signal indications are needed. A distinctive coderate is prescribed for each of several dilferent traffic conditionsandthe receiving apparatus includes decoding devices selectively responsiveto these different code rates so as to establish a distinctive controlfor each such traiiic condition. Since a code rate is effected byinterrupting the current a predetermined number of times per minute andan electromotive force of a frequency corresponding to the code rate isused, tuned circuit arrangements are provided as the decoding means,each such circuit arrangement being tuned for response to a frequencycorresponding to a respective code. Hence when several diiferent coderates are used, several different tuned circuits are required and whenit is necessary to provide an additional indication an additional coderate is provided with an additional tuned circuit.

In view of such code signaling conditions, a feature of my invention isthe provision in railway trafiic controlling apparatus of novel meanswherewith a code more distinctive in character than the usual frequencycode is used and wherewith false operation due to an intermittent opencircuit condition is avoided. 1

Another feature of my invention is the provision of railway trafficcontrolling apparatus incorporating novel and improved means for asimple code signal system for railways.

Again, a feature of my invention is the provision of novel railwaytraffic controlling apparatus for a four-indication cab signal systemand which apparatus avoids the necessity of resonant decoding equipment.I

Still another feature of my invention is the provision of novel railwaytraflic controlling apparatus wherewith one or two additional signalindications can be added to the present standard frequency code signalsystem without requiring additional -code rates.

The above features of my invention, as well as other advantages whichwill become apparent as the specification progresses,are attainedaccording to my invention by providing a code forming means whichimpresses upon a periodically interrupted alternating current any one ofbeing efiected for each of a plurality of diiTerent trafiic conditions.Under onetrafiic condition 4 this special .code forming means causes ina periodically interrupted alternating current the amplitude of thecurrent at the start of each on period to be relatively small and toprogressively increase to a relatively high value at the end of the onperiod, the current dying away abruptly at theend of the on period whenthe circuit is interrupted. Under another traflic condition, the codeforming means causes the alternating current to abruptly rise to arelatively high amplitude at the start of each on period and togradually diminish in amplitude during the on period until it is of arelativelylow value when the circuit is interrupted at the end of the onperiod. That is to say, under one traflic condition the alternatingcurrent has an increasing amplitude code characteristic, and under asecond traflic condition it has a decreasing amplitude codecharacteristic. A slow acting three-position polar relay'is controlledby such coded current and this relay is held at one extreme positionwhen the first mentioned characteristic prevails,

is held at the other extreme position when the second codecharacteristic prevails and is held at its biased third position whenthe alternating current is not provided with either of such-codecharacteristics. This code responsive relay is used to govern theoperating circuits of a multiple indication cab signal or train controldevice.

Additional indications are added to the present frequency code system byincorporating this special code forming means into the usual codetransmitting apparatus of the present frequency code system, with theresult that the special code forming means impresses upon a selectedcode rate the distinctive code characteristics described I shalldescribe two forms of apparatus embodying my invention, and shall thenpoint out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing oneform of apparatus embodying my invention when used for a threeblockfour-indication cab signal system. Figs. 2, 3, c, 5, 6 and 7 arediagrams illustrating the characteristics of the coded current andelectromotive forces effected by the apparatus of Fig. 1. Figs. 8a and8b and 9 are diagrammatic views showing one form of apparatus embodyingmy invention for obtaining two additional indications in a frequencycode cab signal system, Figs. 8a and 8b whentaken together with Fig. 8aplaced at the left disclosing the trackway portion of the apparatus andFig. 9 disclosing the train carried portion of the apparatus.

In each of the several views like reference characters are used todesignate similar parts.

Referring to Fig. 1, the reference characters la and lb designate thetrack rails of a stretch of railway over which traffic normally moves inthe direction indicated by an arrow and which rails are formed by theusual insulated rail joints with a series of consecutive track sectionsof which sections only the one full section D-E and the adjoining endsof the adjacent sections are shown for the sake of simplicity sincethese are sufiicient for a full understanding of my invention. trackcircuit including a source of alternating current connected across therails at the exit end of the section and a track relay connected acrosstherails at the entrance end of the section. The immediate source ofcurrent for'the track circuit of section D- -E is a track transformer TDwhose secondary winding 2 is connected across the rails over wires 3 and4 and whose primary winding 5 is supplied with alternating current fromany convenient source such as a generator whose terminals are indicatedat BX and CK.

Such alternating current is coded in a manner to be made clearpresently. I

The reference character DTR designates a track relay for the trackcircuit of the section next in advance of section D-E. Relay DTR is atwo element alternating current relay having winding 6 of one elementconnected across the rails over wires 1 and 8, and winding 9 of thesecond element of the relay connected directly to the BX and CKterminals of the source of alternating current. Relay DTR is of the typeresponsive to the relative polarity of the currents supplied to its twowindings and is provided with two contact members In and H operable to anormal right-hand position when windings 6 and 9 are energized bycurrents of normal relative polarity and operable to a reverse left-handposition when the relative polarity of the current I supplied to thetrack winding 6 is reversed. When either one or both windings Band 9 aredeenergized the contact members and H occupy a biased mid position.Track relay DTR controls a repeater relay DPR over an obvious circuitincluding contact member ID in engagement with either its normal contactI! or its reverse contact l3. Repeater relay DPR is preferably providedwith slow release characteristics and is used to control the connectionsto primary winding of transformer TD, the arrangement being such thatwhen repeater relay DPR is picked up a normal connection is completedfor primary winding 5 and when the relay is released a reverseconnection is provided for primary winding 5.

Each track section is provided with a to alternately engage a frontcontact I 5 and a back contact 16 as long as the winding'of the coder iseffectively supplied with current. The rate at which contact member I4is operated is preselected and as an aid to the understanding of theapparatus embodying my invention, I shall assume contact member I4 isoperated at'the rate of '75 times per minute, although it is to beunderstood that any other convenient rate may be selected if desired.

The apparatus also includes a code forming means for determining thecode characteristics of the current supplied to the track circuit ofsection D-E. This code forming means comprises a saturable reactor TC,another reactor RC and a full wave rectifier RF. When track relay DTR isheld at its normal right-hand position and repeater relay JDPR is pickedup, current is supplied to primary winding 5 of track transformer TD bya circuit which can be traced from terminal BX of the source ofalternating current over front contact l4--l5 of coder CT, winding ll ofsaturable reactor TC, front contact l8 of relay DPR, primary winding 5of transformer TD, a second front contact 19 of relay DPR and toterminal CX of the current source. The amplitude'of the current flowingin the circuit is determined in part by the impedance of winding ll ofsaturable reactor TC. The impedance of primary winding I! of reactor TCis governed by the flux condition of the magnetic core of the reactorand is high when no direct current flows in secondary winding 20 of thereactor to cause magnetic saturation of the core structure of thereactor and is low when direct current flows in secondary winding 20 toset up a saturated magnetic condition of the reactor core. With trackrelay D TR occupying'its normal position, a circuit is prepared by whichrectified current is supplied to secondary winding 20 of reactor TC,each time front contact I4I5 of that at the end of such on periodmagnetic saturation is-effected for reactor TO. The impedance of primarywinding I! of reactor TC is therefore relatively high at the start ofeach on. period and progressively decreases to a relatively low value atthe end of the on period due to the change effected in the magneticcondition of the core of reactor TC. Consequently, the amplitude of thecurrent supplied to primary winding 5 of I track transformer TD isrelatively low at the D-E includes a code transmitter'or coder CT whichis shown as ,being of the well-known relay type provided with a contactmember l4 operable start of the on period and progressively increases toa relatively high value at the end of the on period. Hence, in turn, theamplitude of the current supplied to the track circuit from secondarywinding 2 of track transformer TD is relatively low at the start of theon period and progressively increases to a relatively high value at theend of the on period. When coder contact I4l5 is operated at the end ofan on period to interrupt the circuit for primary winding 5 the currentabruptly dies away in the track circuit. Also, the rectified currentsupplied to secondary winding 20 is interrupted and the magnetic flux ofreactorTC dies away during the oil code period with the result the abovedescribed operation is repeated each on period of the current. In Fig.2there is illustrated this code characteristic impressed upon the trackcircuit current for section DE when the track relay DTR for the sectionnext in advance occupies its normal position, the amplitude of thecurrent being relatively low at the start of each on period,progressively increasing to a relatively high value at the end of the onperiod and abruptly dying away at the start of the off period. In otherwords, Fig. 2 illustrates the increasing amplitude code characteristicimpressed upon the alternating current during each on'code period.

When track relay DTR occupies its reverse left-hand position, repeaterrelay DPR is picked up as before and current is supplied to the circuitincluding primary winding 5 of transformer TD the same as before.Rectified current is now supplied to secondary winding 20 over a circuitincluding terminal BX, back contact Ml6 oi' coder CT, wire 23, reversecontact I l--24 of relay DTR and thence as previously traced. This timemagnetic saturation is effected for reactor TC during the off period ofthe code, and the circuit for secondary winding 20 is interrupted duringthe on period so that the magnetic saturation gradually decreases duringeach on period. It

.follows that the impedance of primary winding ll of reactor CT is lowat the start of the on code period because of the magnetic saturation ofreactor TC an the impedance of winding ll gradually increases to itshigh value at the end of the on period. Consequently, the currentsupplied to the track circuit through track transformer TD is abruptlystarted at a relatively high value, progressively decreases to a lowvalue at the end of the on period and then dies away from the low valueat the start of the off period. In Fig. 4 there is illustrated thisdecreasing amplitude characteristic impressed upon the track circuitcurrent of section DE when track relay DTR for the section next inadvance occupies its reverse position. In other words, Fig. 4illustrates the decreasing amplitude code characteristic impressed uponthe alternating current each on code period.

When track relay DTR is deenergized and its contact members l and IIoccupy the biased midposition, repeater relay DPR is deenergized andreleased and the connections to the primary winding 5 of tracktransformer 'I'D are pole changed at back contacts 25 and 26 of relayDPR as will be readily understood by an inspection of Fig. 1. Current isnow supplied to primary winding 5 of transformer TD over a circuitincluding terminal BX, back contact I4I6 of coder CT, wire 23, resistor21, back contact 26 of relay DPR, primary winding 5 of transformer TD,back contact 25 of relay DPR and terminal CX. Since the impedance ofthis circuit remains substantially the same, the amplitude of thecurrent flowing therein is substantially uniform throughout the entireon period which in this case is during the period back contact I l-l6 ofthe coder is closed. This current has a substantially uniform amplitudecharacteristic'as compared with the currents of the previous twoconditions. In Fig. 6 there is illustrated this substantially uniformcode characteristic for the track circuit current of section DE whentrack relay DTR for the section next in advance is released.

code characteristics are impressed upon the track circuit current ofsection D--E according to three different traflic conditions in advance,namely, a first traiiic condition which eiiects the normal position oftrack relay DTR causes an increasing amplitude code characteristic forthe track circuit current of section DE, 'a second traflic conditionwhich effects the reverse posi-- tion of relay DTR causes a decreasingamplitude code characteristic for the track circuit current of sectionDE, and a third traflic condition which causes relay DTR to be releasedcauses a substantially uniform amplitude code characteristic for thetrack circuit current of section DE. It is to be observed that the coderate for the track circuit current is the same under each condition.Furthermore, it is to be pointed out that when repeater relay DPR' ispicked up the current supplied to the track circuit of section DE. is ofnormal relative polarity and when relay DPR, is released the current isof reverse relative polarity.

Track relay ETR for section DE is a two element alternating currentrelay, the same as relay DTR for the section inadvance of section DE.Winding 28 of one element of relay ETR is connected across the rails ofsection DE, and winding 29 of the second element of the relay isenergized directly from. the terminals BX and CX of the current source.Consequently when section DE is unoccupied, that is, when a train shownconventionally at TV does not occupy the section, relay ETR is energizedto position its contact members 30 and 3| at the normal right-handposition when current of normal relative polarity is supplied to thetrack circuit, is energized to position contact members 30 and 3| at thereverse left-hand position when current of reverse relative polarity issupplied to the track circuit and is deenergized so that contact members30 and 3| occupy. their biased midposition when train TV occupies thesection to shunt the track circuit. It is to be pointed out track relaysDTR and ETR are inherently slow in their action due to the type of relayand do not follow the on and ofi periods of the coded current suppliedto the respective circuits. That is, each relay DTR and ETR remains inthe position to which it is moved during an on code period during theoff period of the code. If found necessary the track relays DTR and ETRmay be provided with additional slow acting means, several of such meansbeing well-known in the art. Track relay ETR is associated with codeforming means which is the same as that associated with track relay DTRand relay ETR and its associated apparatus govern the supply of codedcurrent to the track circuit for the section next in the rear of sectionDE in the same manner that relay DTR and its associated apparatus governthe supply of coded current to the track circuit for section D-'--E. Itis to be observed that track relays DTR and ETR are not responsive inany distinctive manner to the increasing and decreasing amplitudecharacteristics impressed upon the coded current, but that suchcharacteristics are employed for governing cooperating train carriedapparatus as will now be described.

Still referring to Fig. 1, the train TV has mounted thereon twoinductors 32 and 33 in inductiverelationto rails Ia and lb,respectively, and inductors 32 and 33 are connected together in thewell-known manner so that electromotive It'is to be seen therefore thatthree different" forces induced therein duringthe on code period of thetrack circuit current add their effects. Inductors 32 and 33 areincluded in a receiving circuit in series with a condenser 35 andprimary winding 35 of a transformer TI. A condenser 35 is connectedacross secondary winding 31 of transformer TI and the receiving circuitthat including inductors 32 and 33 and transformer TI is tuned toresonance at the frequency of the track circuit-current. For example,when alternating current of 100 cycles per second is used for the trackcircuit, the receiving circuit of the train is tuned to resonance at 100cycles per second. Hence each on period of the track circuit current isreflected by an electromotive i'orce appearing across secondary winding31of transformer T|, such electromotive force having the same frequencyas the rail-current and having an amplitude proportional to theamplitude of the rail current. In other wordsthe elec tr'omotive'forceappearing across secondary winding 31 possesses the same codecharacteristics as the rail current.

An amplifier including an electron tube 38 is provided. Electron tube 38may be of any one of several well-known types and is shown as a triodehaving a plate 39, a grid 40 and a filament 4|. Filament 4| is normallyheated from the usual train carried 32 volt generator whose terminalsare indicated in Fig. 1 as B32 and N32, a resistor 43 being includedinthe circuit. Grid 40 is included in a grid circuit comprising acondenser-resistance biasing element 42, secondary winding 31 andcondenser 36 in multiple, a portion of resistor 43 and filament 4|.

A motor generator MG whose motor 44 is connected across terminals B32and N32, converts the 32 direct voltage of the train carried gener atorinto a voltage suitable for the plate circuit of tube 38 and which platecircuit extends from positive terminal B300 of generator 45 of motorgenerator MG over primary winding 45 of an output transformer T2, plate39 and intervening tube space to filament 4| of tube 38 and resistor 43to negative terminal N300 of the generator 45-. A primary winding 41 ofa transformer T3 in series with a condenser 48 is connected to the platecircuit in multiple with primary winding 45 of transformer T2. The partsare so proportioned that a given value of plate circuit current normallyflows. That is, when no voltage is applied to grid 40 from the receivingcircuit, the plate current is of a preselected value. Hence theelectromotive forces made to appear portioned to pass the alternatingcomponent of the plate circuit and hence an alternating electromotiveforce is induced in secondary winding 49 of transformer T3 during eachon period of the coded current picked up from the track rails. Theelectromotive force induced in secondary winding 49 is applied to arelay PR through a rectifier 50. Relay PR is a slow release directcurrent relay'and is energized and held picked up in response to thealternating current created in the plate circuit of tube 38 by the codedtrack circuit current, the slow release period of relay PR beingsufficient to bridge the 'off period of the current. I

A secondary winding 5| of transformer T2 is connected to an operatingwinding of a relay MR over a circuit including front contact '52 ofrelay PR and a reactor '53. Relay MR is a for causing a relay to beslow. acting being well-.

known in the art. When an effective electromotive force is made tosuddenly appear across secondary winding 31 of transformer TI and arelatively large'change is suddenly created in the average value of theplate circuit current of tube 38, an electromotive force is induced insecondary winding 5| of transformer T2, it being recalled that thealternating current component of the plate circuit current is by-passedaround primary winding by the path including condenser 48 and winding41. The connections are made such that the electromotive force inducedin secondary winding 5| due to a sudden increase in the average value ofthe plate current energizes relay MR at normal polarity as required tooperate contact member 54 to the normal right-hand position, and theelectromotive force induced in secondary winding 5| due to a suddendecrease in the average value of the plate circuit current energizesrelay MR at reverse polarity as required. to operate contact member 54to its reverse left-hand position. Referring to Figs. 2 and 3, the codecharacteristic for the track circuit current under a first trafficcondition is such that the amplitude of the current gradually increasesfrom a relatively low 1 to a. relatively high value and the currentisabruptly interrupted at the high value. Consequently, the average valueof the plate current changes slowly during the on period and noeffective electromotive force is induced in secondary winding 5| at thestart of each on period, but when at the end of the on period thecurrent is abruptly interrupted at its relatively high value, arelatively large change in the average value of the plate current occurswith the result a corresponding effective electromotive force is inducedin secondary winding 5|. This electromotive forceinduced in secondarywinding 5| is illustrated in Fig. 3 and as stated above it is of apolarity that energizes relay MRat normal polarity. Thus under thisfirst traf'fic condition, relay MR is supplied with an energizingimpulse at the end of each on code period but not at the start of thecode period, and the successive impulses are all of the same polarity.Due to the slow acting characteristics of relay MR, relay MR is operatedto its normal position only after several successive energizingimpulses, but once it is moved to its normal position it remains in thatposition as long as these electromotive forces continue to occur at thepreselected code rate. When such electromotive forces cease, relay MRshortly moves to its biased mid position under the influence of thebiasing element of the relay. Looking now at Figs. 4 and 5, the

code characteristics for the track circuit underv the second trafliccondition is -such as to cause the current to abruptly rise to its highvalue at the start of the on period and to gradually decrease to its lowvalue at the end of the on period. Consequently, a relatively largechange nated to cause signal CS to display a fourth in the plate circuitcurrent is caused at the start of each on period to induce anelectromotive force in secondary winding but substantially noelectromotlve force is induced in secondary winding 5| at the. end ofeach on code period. This electromotive force induced in secondarywinding 5| is illustrated in Fig. 5 and relay MR is successivelyenergized at reverse polarity. Again after several of such energizing,impulses relay MR is operated to its reverse position where it is heldas long as this second code prevails. Looking at Figs. 6 and 7, thesubstantially uniform amplitude code characteristics effected inresponse to the third trailic condition is such that an abrupt change inthe plate current is effected at the start and at the end of each oncode period. The electromotive forces induced in secondary winding 5|are illustrated in Fig. 7 and are alternately of normal and reverse.polarity so that relay MR is alternately energized at normal and reversepolarity. Since relay MR is slow acting and does not respond to a singleenergizing impulse, the energization effected in the relay by oneimpulse is cancelled by the energization effected by the next impulsewith the result that relay MR remains in its biased mid position forthis. third code.

It is to be seen therefore, that relay PR is picked up for each of thethree different codes and relay MR is held at its normal position forthe first code, is held in its reverse position for the second code andat its biased mid position under the third code. Relays PR'and MR areused to control the operating circuits of a train control device such asa cab signal CS capable of displaying any one of four differentindications.

Assuming the train TV occupies section DE as shown in Fig. 1 whentraffic conditions in advance are such that the first codecharacteristic as illustrated in Fig. 2 is-impressed upon the trackcircuit current of section D-E, relay PR is picked up due to thealternating current component of the plate current and relay MR is heldenergized at its normal position. Under these circumstances an operatingcircuit extends from terminalB32 over front contact 58 of relay PR,normal contact 5455 of relay MR, lamp 5!! and to terminal N32, and lamp59 is illuminated to cause cab signa1 CS to display a first indication.

In the event trafiic conditions in advance of section 'D-E are such thatthe code characteri tic is that illustrated in Fig. 4, relay PR ispicked up by the alternating component of theplate current and relay -MRis energized in its reverse position. An operating circuit is formedwhich includes front contact 58 of relay PR, reverse contact 5456 ofrelay MR and lamp 60, and lamp 60 is illuminated to cause signal OS todisplay a second indication. When traific conditions are such that thecode characteristic of the track circuit of section DE is thatillustrated by Fig. 6, relay PR is picked up and relay MR remains at itsbiased position. An operating circuit is now formed including frontcontact 58 of relay PR. contact 54-51 of relay MR and lamp E and thatlamp is illuminated to cause signal CS to d"sp1ay a third indication.Again, when section DE is occupied by a train in advance of train TV andthe track circuit is shunted by such train "n advance, then relays PRand MR of train- TV are deenergized with the result that an operatingcircuit is formed over back contact 62 of relay PR and lamp I63, andthat lamp is illumiindication.

In Figs. 8a and 8b there is disclosed trackway apparatus wherewith thetwo distinctive code characteristics illustrated in Figs. 2 and'4,respectively are added to a three indication frequency code system sothat a total of five different indications are provided. In theembodiment here disclosed the two code rates or code frequencies of 180and 75 are used for two distinctive frequency codes, the decreasingamplitude code characteristic of Fig. 4 is impressed on the 75 code ratefor one additional distinctive code and the increasing amplitude codecharacteristic of Fig. 2 isimpressed on the 180 code rate for aseconjdiadditiOnal"distinctive code. That is, a first 1 indication isreflected by the absence of codedi current (shunted or occupied trackcircult), and the 75 code rate alone is employed for 20,-

the first track circuit to the rear of the occupied section to reflect asecond indication, the 75 code rate with a decreasing amplitudecharacteristic is used for the second track circuit to the rear of theoccupied track circuit to reflect a third indication, and 180 code ratewith an increasing amplitude characteristic is used for the third trackcircuit to the rear of an occupied section to reflect a fourthindication, and the 180 code rate alone is used for the fourth trackcircuit to the rear of an occupied section to reflect a fifth indication.

In Figs. 8a and 8b, the track rails ia and lb of a stretch of railwayover which traffic normally moves in the direction indicated by arrowsare formed by the usual insulated rail joints into sections F, G, H, Jand K, the entrance end of section F and the exit end of section K beingonly shown. Each track section is provided with a track circuitoperative'to supply alternating current coded at any one of the severalcodes described above according to the' tramc conditions in advance ofthat section. The track circuit apparatus includes a code followingtrack relay and two decoding relays in addition to the track relay,repeater relay and code forming means described for the track circuit ofsection DE of Fig. 1. For example, the track circuit apparatus ofsection G'includes as additional apparatus a code following track relayGFS connected across the rails through the usual associatedtransformer-rectifier GR in multiple with the first elemerit of trackrelay GTR, and two decoding relays GA and GL. Relay GFS is thereforeoperated at a rate corresponding to the code rate of the currentsupplied to the track circuit of section G and is operated at such coderate whether or not an increasing or decreasing amplitude characteristicis impressed on the code rate. Relay GFS when operated causes directcurrent periodically interrupted at a rate corresponding to the rate atwhich relay GFS is operated to be supplied to a decoding unit GDU over asimple circuit including contact member 63 of relay GFS. Thedecodingunit GDU may be any one of several forms and is shown conventionallysince its specific structure forms no part of my invention. It issufllcientfor this application to point out that decoding relays GA andGL connected 'to the output side of decoding unit GDU are energized andpicked up according to the code rate .at which the code following relayGFS is operated, the arrangement being such that relay GL is picked upand relay GA is released for the code rate, both relays GL and GA arepicked up for the 180 code rate and both relays GA. and GL are releasedwhen relay GFS is inactive.

It should be pointed out that the coder GCT associated with the trackcircuit apparatus of section G is provided with four contact membersI80a, l88b, 15a and 15b, the contact members 180a and l8llb being eachoperated at the code rate of 180 times per minute and the contact.members la'and 151 being each operated at the code rate of 75 times perminute. Furthermore each coder associated with the apparatus of eachtrack circuit of Figs. 8a and 8b is provided with four contact membersthe same as coder GCT.

It should also be pointed out at this time that in Figs. 8a. and 8b, therelative polarity and code rate of the current supplied to the trackcircuit is utilized to determine the code of the.

tionally at VTI occupies section F to shunt thev track circuit with theresult that track relay FTR is deenergized to occupy its biasedmidposition and code following track relay FFS .is inactive causing thetwo associated decoding relays FA and FL to be released. When the relaysof section F are conditioned to take the positions explained above dueto train VTI occupying the section, alternating current is supplied toprimary winding 64 of track transformer TG for the section G next in therear of section F over a circuit extending from terminal BX, backcontact 65 of relay FA, back contact 66 of relay FL, front contact ofcontact member 1517 of coder FCT, back contact 61 of repeater relay FPR,primary winding 64 of transformer TG, back-contact 88 of repeater relayFPR and to terminal CX. It follows that the track circuit of section Gis supplied with alternating current coded at the '75 code rate and ofuniform amplitude. The

current is of relative reverse polarity since repeater relay FPR isreleased to pole change the connection to transformer TG. Track relayGTR of section G is energized at its reverse or left-hand position,causing repeater relay GPR to be picked up. Code following relay GFS ofsection G is operated at the '75 code rate caus ing decoding relay GLto, be picked up and relay GA to be released.

With the relays of section G thus positioned, the primary winding 68 oftransformer TH of section H is supplied with alternating current of the75 code rate having impressed thereon the decreasing amplitudecharacteristic. The effective circuit includes terminal BX, reversecontact 18 of relay GTR, front contact H of relay GL, back contact 12 ofrelay GA, front contact of contact member 15a of coder GCT, a secondreverse contact 13 of relay GTR, front contact 14 of relay GL, backcontact 16 of relay GA, primary winding 11 ofsaturable reactor GTC ofthe code forming means of section G, front contact 18 of repeater relayGPR, primary winding 68 of transformer TH, front contact 18 of relay GPRand terminal CX. During each off-code period and back contact of contactmember 15a of coder GCT is closed, current flows over the previouslytraced circuit up to contact member 1511, thence over back contact ofcontact member 15a, reverse contact 88 of relay GTR, one arm ofrectifier GRF, reactor GRC, secondary winding 8| of reactor GTC, and asecond arm of rectifier GRF to terminal CX, and. rectified current flowsin the secondary winding 8| of reactor GTC to saturate that reactorduring each off code period with the result that a decreasing amplitudecharacteristic is impressed upon the coded'current supplied totransformer TH and in turn supplied to the track circuit of section H inthe manner fully explained in connection with Fig. 1. Since the repeaterrelay GPR, is picked up the current supplied to section H is of normalrelative polarity.

With alternating current of anormal relative polarity of the '75 coderate supplied to section H, the second section in the rear of theoccupied section F, track relay HTR is energized at its normal positioncausing repeater relay HPR to be picked up, and code following relay HFSis operated at the '75 code rate causing decoding relay HL to be pickedup and relay HA to be released. Under such circumstances th primarywinding 82 of track transformer TJ of section.J is supplied withalternating current of 180 code rate having impressed thereon anincreasing amplitude characteristic. The circuit includes terminal BX,normal contact 83 of relay H'IR, front contact 84 of relay HL, backcontact 85 of relay HA, front contact of contact member |88b of coder'HCT, normal contact 86 of relay H'I'R, front contact 81 of relay HL,back contact 88 of relay.HA, primary winding 88 of saturable reactorHTC, front contact 90 of repeater relay HPR, primary winding 82 of tracktransformer TJ, front contact 9| of relay HPR and terminal CX. Duringeach on period that the front contact of contact member l80b is closedcurrent also flows over the previously traced circuit up to contactmember |80band the code rate, causing track relay 'J'IR. to

be energized .atnormal polarity and code following relay JFS to beoperated at the 180 code rate to pick up both decoding relays JA and JL.

Under such condition of the relays for section J, the third section tothe rear of occupied section F, the track circuit of section K, thefourth section to the rear of the occupied section, is supplied withcurrent of the 180 code rate alone, the effective circuit extending fromterminal CX over normal contact 85 of relay JTR, front contact 86 ofrelay JL, front contact 81 of relay JA,

front contact of contact member l88a of coder JCT, primary winding 88 ofreactor JTC, front contact 88 of repeater relay JPR, primary winding 94of transformer TK and front contact I88 of relay JPR to terminal CX.Since the secondary winding of reactor JTC is not supplied withrectified current then the circuit for supply ing alternating current tosecondary winding 85 of track transformer TX is of substantially uniformimpedance and the track circuit current of section K is of the 180. coderate, with a substantially uniform amplitude throughout the code Period.

Since section K is supplied with current of 180 code rate and of normalrelative polarity, it is apparent that the track relay and the decodingrelays (not shown) of section K are positioned the same as thecorresponding relays of. section J with the result that the section nextin the rear current increases andof the other polarity when the platecurrent decreases. Consequently relay MRI is operated in the usualmanner due to of section K is supplied withcurrent of the same codecharacteristics as the current supplied to section K.

Referring to Fig. 9, the train. carried apparatus for cooperating withthe track apparatus of Figs. 8a and 8b includes inductors 32 and 33 anda first stage electron tube 38 the same as in Fig. 1, except that thesecondary winding 5| of transformer T2 is, in Fig. 9, connected to thegrid circuit of a second electron tube IOI having a plate I02, a gridI03 and a filament I04. The

filament I06 of tube IN is heated in series with the filament M of tube38 and the'grid I03 is connected to secondary winding SI of transformerT2 as mentioned above. The plate circuit for tube IOI involves terminalB300 of the motor generator MG, primary winding I05 of a transformer T3,plate I02 and intervening tube space to filament I04 of tube WI, andthence over filament 5i and resistor 43 to terminal N300. Primarywinding I05 of transformer T3 is by-passe'd by a condenser I06, and asecondary winding I01 of transformer T3 is connected to a three-positionpolar relay MR through a reactor 53, relay MR being of the samecharacter as the corresponding relay of Fig. 1. A code following relayMRI is also connected to secondary winding I 0I. 1"

Relay MRI is a polar code following relay of the usual well-known formwhose contact member I00 remains in the position to which it is lastmoved when the relay is deenergized. Direct current is alternatelysupplied to the two portions of a primary winding I00 of a decodingtransformer T4 when relay MRI is alternately energizedat normal andreverse polarity causing operation-of its contact member I03 with theresult that an alternating electromotive force is induced in secondarywinding I I0 of transformer T0 the frequency of which electromotiveforce corresponds to the rate at which relay MRI is operated. Secondarywinding I I0 is connected to two decoding circuits one of which includesin v series a condenser III and a reactor H2, and

such alternate polarities of the electromotive forces induced insecondary winding I01 and both decoding relays AI and LI are picked up.Relay MR which is .a slow acting polar relay is not effectivelyenergized by such electromotive forces of alternate polarity for thereasons explained in full in connection with the polar relay MR ofFig. 1. With both relays-LI and AI picked up, closing front contacts H6and Ill, respectively, an operating circuit for lamp II8 of signal CSIis completed, and that lamp is illumi-' nated to cause signal CSI todisplay a first or clear signal indication to indicate that there are atleast three unoccupied sections in advance of' the train. I

When the train having mounted thereon the apparatus of Fig. 9 enterssection J where the track circuit current is of the 180 code rate with vincreasing amplitude characteristic, a co r reperiod and an effectiveelectromotive force is induced in secondary winding -I0l of transformerT3 only at the end of the on period. These electromotive forces are allof the same polari'y and relay MRI remains at one position and bothdethe other of which circuits includes a'reactor H3.

A decoding relay AI is connected across a portion of reactor II2 througha rectifier H4, and a second decoding relay LI is connected'to reactor II3 through a rectifier I I5. The circuit including reactor H3 isnon-tuned and relay LI is efiectively energized and picked up when relayMRI is operated at a rate corresponding either to the '75 or 180 coderate. The circuit ineluding condenser III and reactor H2 is tuned sothat'relay AI is effectively energized and picked up only when relay MRIis operated at the rate corresponding to the 180 code rate. Relay MRtogether with the decoding relays AI and LI govern a, five-indicationcab signal CSI.

Assuming, the train on which the apparatus of Fig. 9 is mounted isoperating in section K of Fig..8b, which track circuit is supplied withcurrent of the 180 code rate and uniform amplitude characteristic, acorresponding electromotive force is picked up by the inductors 32 and33 and amplified at tubes 30 and IN. As a result of such amplificationof the electromotive force there is induced in secondary winding I01 ofcoding relays Li and AI are released because relay MRI is notoperated byelectromotive forces all of the same polarity. After a few suchelectromotive forces relay MR is moved to its reverse position and anoperatingcircuit is formed from terminal B over back contact II 9 ofrelay LI, contact 54-56 of relay MR, lamp I20 and to terminal C, andlamp I20 is illuminated to cause signal CSI to display a second orapproach medium signal indication.

When the train advances to enter section H i where the track circuitcurrent is of the 75 code rate with a decreasing amplitudecharacteristic,

the operation of the train carried apparatus is the 1 same as in sectionJ except for the fact that relay MR is moved to its normal position dueto the polarity of the electromotive force induced in secondary windingI0'I. An operating circuit is now formed including back contact I I 9 ofrelay LI, left-hand contact 5455 of relay MR and is operated at acorresponding code rate and relay LI is picked up and relay AI isreleased. Also relay MR is inactive. An operating circuit now is formedincluding front contact III; of relay LI. back contact I22 of relay AIand lamp I23. and that lamp is illuminated to cause signal CSI todisplay a fourth or approach signal indication.

In the event the train VTI remains in section F and the train on whichthe apparatus of Fig. 9 is mounted enters section F behind train VTI.the track circuit current is shunted by train VT I so that relays MRIand MR are both deenergized. An operating circuit now including backcontact N9 of relay Li and contact 54-57 of relay MR and lamp E24 iscompleted, and lamp I24 is illuminated to cause signal CSI to display afifth or slow speed signal indication.

It is to be observed that although wayside signals are not shown ineither Fig. 1 or Figs. 8a and 8b, it is clear that wayside signals maybe provided andcontrolled by the trackway apparatus shown in thedrawings.

It is to be seen therefore that I have provided simple railway trafiiccontrolling apparatus incorporating novel means for a code signal systemusing distinctive code characteristics. have provided novel railwaytraffic controlling apparatus wherewith additional indications can beadded to the present frequency code system without the necessity ofadditional code rates.

Although I have herein shown and described only two forms of railwaytraffic controlling apparatus embodying my invention, it is understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim is:

i. In railway trafiic controlling apparatus the Also I combinationcomprising, a track section, a source of alternating current, a circuitto connect said source to the rails of said section, means toperiodically interrupt said circuit to cause the current supplied to therails to have alternate on and oii periods, code forming means having avariable reactance included in said circuit and effective to cause anincreasing amplitude or a decreasing amplitude of the alternatingcurrent each on period according as said reactance isprogressivelydecreased or increased during the on period, and traflilccontrolled means effective under one traffic condition to progressivelydecrease said reactance during each on period and effective underanother traflic condition to progressively increase said reactanceduring each on period 2. In railway traiiic controlling apparatus thecombination comprising, a track section, a source of alternatingcurrent, a circuit to connect said source to the rails of said section,means to periodically interrupt said circuit to cause the currentsupplied to the rails to have alternate on and off periods, code formingmeans having a variable reactance included in said circuit and effectiveto cause an increasing amplitude or a decreasing amplitude of thealternating current each on period according as said reactance isprogressively decreased or increased during the On period, trafiiccontrolled means effective under one traffic condition to progressivelydecrease said reactance during each on period and effective underanother trafiic condition to progressively increase said reactanceduring each on period, and receiving means coupled to therails -ofsaidsection responsive to such alternating on and off periods, codeforming means including a variable reactance element interposed in saidcircuit and said code forming means effective when supplied with currentduring each on period to progressively decrease the reactance of saidelement to impress an increasing amplitude on the alternating currentsupplied to the rails, and trafiic controlled means to supply current tosaid code forming means during each on period in response to a giventraffic condition in advance of said section.

4. In railway trailic controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to'the rails of said section, means to penodically interruptsaid circuit to cause the current supplied to the rails to havealternate on and off periods, code forming means including a variablereactance element interposed in said circuit and said code forming meanseffective when supplied with current during each off period to cause aprogressively increasing value of the reactance of the element duringthe on period to impress a decreasing amplitude 0n the alternatingcurrent supplied to the rails, and traflic controlled means to supplycurrent 'to said code forming means during each off period in responseto a given traffic condition in advance of said section.

5. In railway traflic controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to the rails of said section, means to periodicallyinterrupt said circuit to cause the current supplied to the rails tohave alternate on and oil periods,'code forming means having an elementthe impedance of which progressively decreases or increases according asunidirectional current is supplied to a winding of the code formingmeans or is interrupted therefrom, said element interposed in saidcircuit to impress an increasing or a decreasing amplitude codecharacteristic on the alternating current according as the impedance ofsaid element is made to progressively decrease or increase during eachon period, and traffic controlled means to supply unidirectional currentto said winding during each on period only under one traflic conditionand to supply such unidirectional cur- I rent to the winding during the05 period only under another traflic condition.

6. In railway trafflc controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to the rails of saidsection, means to pcriodically interruptsaid circuit to cause the current supplied to the rails to havealternate on and off penods, code forming means including a saturablereactor having a primary winding and a secondary winding and saidprimary winding interposed in said circuit, a first traflic controlled.means to supply unidirectional current to said secondary winding duringeach on period of the alternating current to progressively decrease theimpedance of said primary winding during each on period and impress anincreasing amplitude characteristic on the alternating current inresponse to a first traflic condition in advance of the section, and asecond traflic controlled means to supply unidirectional current to saidsecondary winding during each off period of the alter-.

nating current to progressively increase the impedance of said primarywinding during each on period and impress a decreasing amplitudecharacteristic on the alternating current in response to a secondtraflic condition in advance of the section.

7. In railway trafiic controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to the rails of said section, means to periodicallyinterrupt said circuit to cause the current supplied to the rails tohave alternate on and off periods, a code forming means including asaturable reactor' provided with a first and a second winding with saidfirst winding interposed in said circuit, a first trafilc controlledmeans to supply unidirectional current to said second winding duringeach on period of the alternating current to progressively saturate thereactor and cause each on period of the alternating current to becharacterized by an increasing amplitude, a second traffic controlledmeans to supply unidirectional current to said second winding duringeach off period of the alternating current to saturate said reactor andwhich saturation dies away during the next on period to cause each onperiod of'the alternating current to be characterized by a decreasingamplitude, and receiving means coupled to the rails of said sectionresponsive to such alternating current andefiectively influenced to onecondition by said increasing amplitude characteristic and to anothercondition by said decreasing amplitude characteristic.

8. In railway trafiic controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to the rails of said section to supply cur rent'thereto, acoder'having a front contact interposed in said circuit to cause thealternating current to have alternate on and off periods, a saturablereactor having a first winding interposed in said circuit, meansresponsive to trafiic conditions in advance of said section andincluding a contact member moved to a first and a 'second position inresponse'to a first and a second traffic condition respectively, meansincluding a front contact of said coder and the first position of saidcontact member to supply unidirectional current to a second winding ofsaid reactor to magnetically saturate the reactor during each on periodof the alternating currentand impress an increasing amplitudecharacteristic on the alternating current, and means including a backcontact of said coder and the second position of said contact member tosupply unidirectional current to said second winding to magneticallysaturateof alternating current, a circuit to connect said source to therails of said section to supply current thereto, a coder having afrontcontact interposed in said circuit to cause the alternating current tohave alternate on: and off periods, a saturable reactor having a firstwinding interposed in said circuit to control the impedance of thecircuit and a second winding to control the magnetic saturation of the-reactor; trafllc controlled means operable to a-first, a second and athird position in response to a, first, a second and a third trafficcondition respectively in advance of said section; means including afront contact of said coder and the first position of said trafliccontrolled means to supply unidirectional current to said second windingto provide an increasing amplitude characteristic of the alternatingcurrent in response to said firsttraffic condition, means including aback contact of said coder and the second position of said trafiiccontrolled means to supply unidirectional current to said secondwindingto provide a decreasing amplitude characteristic of thealternating current in response to said second trafiic condition, andmeans including the third position of said traflic controlled means todeenergize said second reactor winding to provide a uniform amplitudecharacteristic of the alternating current in response to said thirdtrafiic condition.

10. In railway traffic controlling apparatus the combination comprising,a track section, a source of alternating current, a circuit to connectsaid source to the rails of said section to supply current thereto, acoder having a front contact interposed in said circuit to cause thealternating current to have alternate on and off periods of apreselected code rate, a saturable reactor having an impedance windinginterposed in said circuit and provided with a saturating winding;traflic controlled means operable to a first, a second or a thirdposition in response to a first, a second or a third traflic conditionrespectively in advance of said section; means including a front contactof said coder and the first position of said trafiic con-trolled meansto supply unidirectional current to said saturating winding to cause aprogressing decrease in the impedance of said impedance winding each onperiod of said coder to provide an increasing amplitude codecharacteristic of the alternating current in response to said firsttrafiic condition, means including a back contact of said coder and thesecond position of said traffic control led means to supplyunidirectional current to said saturating winding to cause a progressingincrease in the impedance of said impedance winding each on period toprovide a decreasing amplitude code characteristic of the alternatingcurrent in response to said second traffic condition, and meansincluding the third position of said trafiic controlled means to bypasssaid circuit around said impedance winding to provide a uniformamplitude code characteristic of the alternating current in response tosaid third trafiic condition.

11. In railway traffic controlling apparatus the combination comprising,a track section; trafiic controlled means to supply to the rails of thesection alternating current periodically interrupted at a preselectedrate and operative to provide an increasing amplitude codecharacteristic of the current under a first traflic condition, adecreasing amplitude code characteristic of the current under a secondtraflic condition and an uniform amplitude code characteristic of thecurrent under a third trafiic condition; a train to travel said section,receiving means responsive to such alternating current and mounted on.the train in inductive relation to the rails, and train carriedsignaling means coupled to said receiving means and including athree-position relay effectively operated to a. first position inresponse to periodically interrupted alternating current of saidincreasing amplitude code characteristic, to a second position inresponse to periodically interrupted alternating current of saiddecreasing amplitude code characteristic and to a third position inresponse to periodically interrupted alternating current of said uniformamplitude code characteristic.

12. In railway trafilc controlling apparatus the combination comprising,a track section; traffic controlled means to supply to the rails of the.

position, a reverse position and a biased position; and amplifying meanson the train to couple said receiving means to said relay and effectiveto supply to the relay energizing impulses of normal polarity forpositioning the relay at its normal position when the alternatingcurrent supplied to the rails is provided with said increasing amplitudecharacteristic, energizing impulses of reverse polarity for positioningthe relay at its amplitude code character- 15. In railway trafiiccontrolling apparatus the combination comprising, a track section, asource of alternating current, a coder provided with two reverseposition when the alternating current supplied to the rails is providedwith said decreasing amplitude characteristic and energizing impulsealternately of normal and reverse polarities for holding the relay atits biased position when the alternating current supplied to the railsis provided with said uniform amplitude characteristic.

13. In railway trafiic controlling apparatus the combination comprising,a tracksection, circuit means to' supply to the rails of the sectionalternating current periodically interrupted at a preselected rate,trafiic controlled code forming means including a'saturable reactorinterposed in said circuit means to impress on said alternating currentan increasing or a decreasingamplitude characteristic in response to afirst or a second trailic condition respectively, a train to travel saidsection, and train carried receiving apparatus including an inductormounted on the train in inductive relation to the rails, a polar relay,amplifying means coupled to said inductor and connected to said relayand operative to supply to the relay successive energizing impulses oione polarity when the alternating current is characterized by saidincreasing amplitude and of the opposite polarity'when the alternatingcur- .rent is characterized by said decreasing amplied code rates,trafiic controlled means including said contact members to connect saidcurrent source to the rails of said section to supply to the railsalternating current of a first or a second code rate in response to afirst or a second traflic condition in advance of the sectionrespectively, a code forming means including a saturable reactor, andother tramc controlled means including a selected one of said contactmembers and said code forming means to connect said current source tothe rails of said section to supply to the rails alternating current ofa preselected one of said code rates further characterized by aprogressive change in the amplitude of the current during each oncode-period.

contact members operated at different preselected code rates, trafllccontrolled means including said contact members 'toconnect said currentsource to the rails of said section to supply to the rails alternatingcurrent of a first or a second code rate in response to a first or asecond tramc condition in advance of the section respectively,

'a code forming means including a saturable re-.

actor, other trafilc controlled'means including a selected ore of saidcontact members and said code forming means to connect said currentsource to the rails of said section to supply to the rails alternatingcurrent of a preselected one of said code rates further characterized bya progressive change in the amplitude of the current during each on codeperiod, a train to travel said section, a receiving circuit mounted onthe train responsive to such codedalternatingcurrent, a first and asecond code responsive relay mounted on the train, train carriedamplifier to couple said receiving circuit to said relays and effectiveto operate said first relay in response to said'first and second codesand to effectively energize said second relay in response to said thirdcode, and a train carried train control device governed by said firstand second relays.

16. In railway trafilc controlling apparatus the combination comprising,a track section, a source of alternating current, a coder provided withtwo contact members each operated at a distinctive code rate, trafficcontrolled means including said contact members to connect said currentsource to the rails of said section to supply to the rails alternatingcurrent of a first or a second code rate in response to a first and asecond traflic condition respectively, a code formingmeans including asaturable reactor having a first and a second winding, other trafliccontrolled means including a selected one of said contact members andsaid first reactor winding to connect said current source to the railsof said section to supply to the rails current of said selected one ofsaid code rates, means including said selected contact member to supplyunidirectional current to said second reactor winding during each oilcode period to impress upon said coded current ofsaid one code rate adecreasing amplitude characteristic, still other trafllc controlledmeans including the other contact member and said first reactor windingto connect said current source to the rails of said section to supply tothe rails current of the other code rate, and means including said othercontact member to supply unidirectional current to said second reactorwinding to impress on the coded current of said other code rate anincreasing amplitude characteristic.

17. In railway trailic controlling apparatus the combination comprising,a track section, a'source of altenating current, a circuit to connectsaid source to the rails of said section, means to ,periodicallyinterrupt said circuit to cause the current supplied to the rails tohave alternate on and off periods, and trafllc controlled meansassociated with said circuit and including a vari- 'able element tocause the alternating current to have an increasing amplitudecharacteristic each on period under one tra-filc condition in advance ofthe section and to have a decreasing amplitude characteristic each onperiod under another trafiic condition in advance of the section.

combination comprising, a circuit, supply means connected to saidcircuit and effective to supply the circuit with alternating currenthaving alternate on and off periods, code forming means associated withsaid supply means and effective to cause the alternating current to becoded by an increasing amplitude characteristic or by a decreasingamplitude characteristic each on period according to a first or secondcondition of the coueforming means, control means op- 10

